This invention relates generally to the onsite purification plant supplying high purity (HP), and ultra high purity (UHP) chemicals, industrial, and specialty gases.
One of the major concerns in the semiconductor manufacturing industry at every stage of the manufacturing processes is contaminants. Contaminants introduced into a manufacturing process may change the final product properties drastically. As the result, a production line may be stopped and closed for decontamination. That may lead to: first, disqualification of a significant amount of already manufactured electronic devices and second, it may stall the production for a period of time. Both events may be translated into significant losses in revenue for electronics fabrication facilities. That is why the issue of production line contamination is important to address from the very initial steps in the electronics production processes.
Number of publications deals with onsite purification plants and supply of chemicals and specialty gases. Some publications concern with better mixing of chemicals as, for example, described in U.S. Pat. No. 6,616,014, EP 1127658, U.S. Pat. No. 6,923,568, EP 1305107, and U.S. Pat. No. 6,200,414B1. Different systems and methods are offered to minimize the change in composition of chemical solutions delivered and used in manufacturing processes of electronic devices. In addition, U.S. Pat. No. 6,200,414B1 for example, offering the system and method for controlling temperature and pressure of the chemicals used in wafer etching processes. This patent suggests continuous recirculation of the chemicals through a bypass line when the tool is in the process of changing wafers and the flow of chemicals should be stopped. The described system was designed with high turn down ratio. On the other hand, the suggested system utilizes chemical solutions which are reusable and may be recollected in the main chemical tank over and over again. Minor cleaning of the returned solution may be required but no major purification devices and systems were discussed.
Other publications concern with purification of chemicals and gases.
For example, U.S. Pat. No. 7,371,313 patent offers the invention of ammonia purification. The ammonia stream is produced at ammonia generation facility and follows the sequence of purification steps until it reaches the desired purity level. All purification steps may be separate or connected to each other to handle the desired UHP product purity at the end of the purification process. The system works for a constant flow of crude ammonia stream and would have a limited turn down ration with respect of preservation of the final product purity.
Another system is offered in US 2007007879A. The system supplies a purified product to the point of use based on vaporization of the product liquid fraction and delivery of the product vapor fraction to the point of use. The system utilizes one step purification stage and is applicable for UHP delivery when the liquid fraction is already at UHP level and only possible concentrated heavy impurities such as heavy hydrocarbons need to be avoided from the accidental delivery in to a manufacturing process. Such a system is more suitable for product delivery from transportable units such as ISO modules, cylinders, etc. Onsite purification system most likely would be using permanent purification unit such as adsorption beds and distillation columns to purify crude product stream.
EP 0949470 and U.S. Pat. No. 6,032,483 suggest a system for delivering purified vapor stream of liquid chemicals to a point of use. The system suggest a plurality of columns connected to each other where one of the arrangements is when the next (second) column receives a heavy liquid fraction from the preceding column for further product purification. UHP HCl for use in semiconductor manufacturing processes is prepared onsite by drawing HCl vapor from a liquid HCl reservoir and scrubbing the filtered vapor in a low=pH aqueous scrubber as suggested in TW 306021. The vapor stream is put through the scrubber before entering the line supplying it into the manufacturing process.
Patent US 2002128148A1 is describing a system to purify or decontaminate fluid ammonia. The system consists of a plurality of adsorbent beds where the contaminants accumulate. A portion of the ammonia stream is decomposed into hydrogen and nitrogen and the hydrogen is used to regenerate adsorbents. The described system does not let one to turn down the system changing production based on the manufacturing process demand rather then switch a number of adsorbent beds off in the case when the system has a plurality of such beds. The turn down ratio of the system may not vary in a wide range assuming that set product purity range is preserved when the system has only one bed. In addition, a portion of the product is used for decontamination of the beds which makes the system less efficient.
U.S. Pat. No. 6,372,022B1 describes a method and apparatus for purification and production of UHP chemicals based on ionic purifiers. The invention suggests a continuous process of purification and production UHP chemicals stream to be used in manufacturing processes and contaminated water stream carrying out contaminants removed from the product stream. The system assumes continuous delivery of the product and does not address the issue of the system turn down ratio.
U.S. Pat. No. 6,395,064 and WO 0145819 offered a system for vaporization and purification of a gas to UHP level to be used in semiconductor manufacturing process. The purified gas is routed to a buffer tank and then to a point of use in the manufacturing process.
U.S. Pat. No. 7,297,181 and WO 06005990 introduced a system for ammonia purification where the system uses different means of ammonia purification such as adsorption and distillation to purify ammonia. The system also suggests a purified product storage tank equipped with vaporizers to vaporize liquid product and to supply it to the point of use on demand. In general, once the storage tack is full and there is no demand of the product, the system has to stop UHP ammonia production since there is no place to put the product. Typically, a restart of the system involved spikes in product purity which may be unacceptable for semiconductor manufacturing process. Therefore, the portion of the product and most important the restart product supply time may be inadequate for the end user.
Some publications concern with control systems providing automated adequate control to obtain the desired product purity. For example, a control system for distillation tower was suggested in CN 2011006332. The system utilizes and intelligent check machine a DCS system and onsite bus wherein the check machine obtains historical process data from DCS real-time database and controls the output value for liquid/vapor (L/V) ratio in the distillation tower. Therefore, the said L/V ration is managed and changed constantly to maintain and confirm high purity stable operation via system dynamic control. At the same time, one should note that the purity range may change if the flow rates in the distillation tower are below the minimum threshold.
However, those teachings typically do not offer a system with futures such as high turn down ratio and consistent range of supplied substances purity present simultaneously.
Thus, there is a significant need for an onsite purification plant (or system; plant and system are exchangeable) and methods which can deliver HP and UHP product within the predetermined purity range at variable product flow rates simultaneously. That is, system and method of onsite purification are needed which would combine both futures of delivering purified product at predetermined consistent purity range with high onsite purification plant turn down ratio.